The invention relates to a method for flow-forming a part having an inner collar and an outer collar, which surrounds the inner collar, as well as an apparatus for flow-forming such a part.
For numerous purposes in gear technology gear parts are required having a radially inner, cylindrical sleeve section and an outer, cylindrical sleeve section surrounding the latter. Such gear parts with a so-called double collar or hub can be manufactured in various ways according to the prior art. Thus, such parts can e.g. be manufactured by casting or forging methods. However, these methods are limited with regards to the shaping variety and are only economic for the manufacture of large batches.
In the case of smaller batches such gear parts are frequently welded together from intermediate members. However, a shape-precise welding is scarcely possible, so that with this production procedure a complicated reworking of the welded part is often necessary. It is finally known to manufacture such gear parts in non-cutting manner by flow-forming. In this case in a first setting in a flow-forming machine a first hub is shaped by splitting and/or upsetting processes on a first spinning chuck. A reshaping of the workpiece on a flow-forming machine with a second spinning chuck adapted to the outer collar is then necessary and in a further method step the second outer collar is shaped. Conventional flow-forming machines are used for this method.
The object of the invention is to provide a method and an apparatus with which parts having a double collar or sleeve structure can be manufactured particularly economically.
According to the invention this object is achieved firstly by a method having the features according to claim 1 and secondly by an apparatus having the features of claim 7. Preferred embodiments of the invention are given in the dependent claims.
The invention therefore relates to a method for the flow-forming of a part having an inner collar and an outer collar, which surrounds the inner collar, wherein
a workpiece with a workpiece section running in a radial direction is clamped to a spinning tool in a flow-forming machine,
the workpiece is rotated and at least one spinning roller is radially infed,
through the spinning roller material is partly separated on the radial workpiece section,
the separated material is radially formed against the spinning tool and the inner collar is shaped,
a sliding sleeve displaceably mounted on the spinning tool is engaged axially over the inner collar and
with a spinning roller further material of the radial workpiece section is formed and pressed against the sliding sleeve, the outer collar being shaped.
One aspect of the invention is based on the fact that the workpiece with the two collars can be manufactured in a single setting. Apart from the spinning tool, at least one sliding sleeve is provided on said spinning tool, which following the shaping of the inner collar is engaged over the latter. In this position the sliding sleeve constitutes a second spinning tool, against which can be formed the second collar or the second, cylindrical circumferential section. This permits an efficient and therefore cost-effective manufacture of such gear parts.
In the sense of the invention the separation of the material for forming the collar can take place by flow-turning (the reduction of thickness leads to an elongation) or splitting/cutting, preference being given to the latter due to the low force expenditure and the reduced work-hardening. The spinning roller can be infed up to the spinning tool, so that the collar is finally shaped in clearly defined form and in complete manner between the spinning roller and the spinning tool.
A particularly dense, highly hardened material structure can be obtained in the collar. Alternatively a gap can be left between the spinning roller and the spinning tool, so that lower infeeding forces are required. However, then in the case of reduced hardening a material burr forms, which must be subsequently worked off.
According to the invention a particularly large multiplicity of shapes can be obtained in that during the forming of the outer collar a web of the radial material section is left behind and is subsequently reshaped.
According to a preferred procedure according to the invention the web is initially thickened and then provided with a profile. As a function of the desired final shape the thickening as an intermediate shape can in cross-section be oval, a symmetrical or asymmetrical drop, a cone or a rectangle. Such a thickening can then be further reshaped in advantageous manner and in particular provided with external teeth or a poly-V profile. The remaining circular blank web can be formed both to the side of the two collars formed for forming a third collar or on the opposite side. Besides external teeth it is also possible to shape on the reshaped web a corresponding inner profile, e.g. friction disk clutch teeth.
According to a preferred variant of the invention the inner collar is provided with an inner profile. For this purpose the spinning tool is provided with a corresponding outer profile, against which is spun the material split off or removed from the starting workpiece and is formed to a collar. Correspondingly an inner profile can be provided on the outer collar, in that the sliding sleeve is provided on its outside with a corresponding profiling. It is also possible by means of a correspondingly constructed sliding sleeve to stamp or cut in contouring on the outside of the inner collar.
According to a further development of the invention it is particularly advantageous to provide the outer collar with an outer profile, which can in particular be a tooth system or a poly-V contour.
According to the invention an extremely economic method is obtained in that the inner collar and/or the outer collar undergoes shaping in a radial infeed by means of a spinning roller, which has an outer contour corresponding to a desired collar shape. Through a simple replacement of such a spinning roller, it is possible to modify in simple manner the contour of the collar to be shaped. This is an important economic advantage particularly when manufacturing small and medium-sized batches.
On the basis of a flow-forming apparatus with a spinning tool, on which a workpiece is clamped, a drive for the rotary driving of the workpiece clamped to the spinning tool and at least one spinning roller with a separating edge for splitting off material and forming collars, according to the invention this object is also achieved in that a sliding sleeve is provided, which at the spinning tool is mounted in axially displaceable manner between a first position, in which the sliding sleeve is spaced from the workpiece for forming the inner collar, and a second position in which the sliding sleeve is located at the workpiece and embraces the shaped inner collar, and that an outer circumferential area of the collar is constructed in accordance with the inner contour of the shaped outer collar.
This flow-forming machine is suitable for performing the method according to the invention, leading to the advantages associated therewith. The starting workpiece can be in the form of sheet metal circular blanks, preshaped sheet metal parts or forged or cast workpieces made from the most varied materials.
According to a preferred embodiment of the invention there are two axially facing spinning tools between which the workpiece can be clamped. Thus, forming processes can be carried out on either side of the workpiece, so as to permit a particularly large variety of shapes.
According to the invention this is further developed in that on the two spinning tools is in each case provided a sliding sleeve. Thus, a double collar or sleeve structure can be constructed on both sides of the workpiece.
Another preferred embodiment of the invention comprises placing several sliding sleeves in telescopic manner on one spinning tool. Thus, two, three or more sliding sleeves can be arranged coaxially within one another, so that three, four or correspondingly more cylindrical collar areas can be constructed on one side of the workpiece.
The above-described invention can not only be used for the manufacture of gear parts, but also all other flow-formed parts, in which a double or multiple collar or sleeve structure is desired on one side of a workpiece. The clamping of the workpiece on the spinning tool can, as a function of the workpiece shape and the forming forces, take place by an axially acting overarm, a radially acting jaw chuck, a magnetic or vacuum clamping device, etc., or a combination of such clamping means.